Fallback to local in-memory counter if Redis is unavailable (#15)

* Fallback to local in-memory counter if Redis is unavailable

* Example with in-memory fallback; add Prometheus /metrics endpoint

* Improve naming, add example CURL command

* Fix passing custom redis client

* Update go-redis to @latest

* Set DisableIndentity to workaround SETINFO error

redis mget failed: ERR Unknown subcommand or wrong number of arguments for 'setinfo'. Try CLIENT HELP.

* Run CI test 10x times

* Test against in-memory fallback disabled

* CI: Print ulimit

* Adjust timeout values

* Tweak the reconnect interval

* Relax the default fallback timeout a bit

.github/workflows/ci.yml

@@ -33,5 +33,8 @@ jobs:
       - name: Build example
         run: cd ./_example && go build -v ./
 
+      - name: Check ulimit
+        run: ulimit -n
+
       - name: Test
-        run: go test -v ./...
+        run: go test -v -count=10 ./...

_example/go.mod

@@ -5,10 +5,26 @@ go 1.22.5
 replace github.com/go-chi/httprate-redis => ../
 
 require (
+	github.com/go-chi/chi/v5 v5.1.0
+	github.com/go-chi/httprate v0.12.0
+	github.com/go-chi/httprate-redis v0.3.0
+	github.com/go-chi/telemetry v0.3.4
+)
+
+require (
+	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
-	github.com/go-chi/chi/v5 v5.1.0 // indirect
-	github.com/go-chi/httprate v0.11.0 // indirect
-	github.com/go-chi/httprate-redis v0.3.0 // indirect
+	github.com/golang/mock v1.6.0 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
+	github.com/prometheus/client_golang v1.19.0 // indirect
+	github.com/prometheus/client_model v0.6.1 // indirect
+	github.com/prometheus/common v0.52.3 // indirect
+	github.com/prometheus/procfs v0.13.0 // indirect
 	github.com/redis/go-redis/v9 v9.6.1 // indirect
+	github.com/twmb/murmur3 v1.1.8 // indirect
+	github.com/uber-go/tally/v4 v4.1.16 // indirect
+	go.uber.org/atomic v1.11.0 // indirect
+	golang.org/x/sys v0.19.0 // indirect
+	google.golang.org/protobuf v1.33.0 // indirect
 )

_example/main.go

@@ -9,31 +9,53 @@ import (
 	"github.com/go-chi/chi/v5/middleware"
 	"github.com/go-chi/httprate"
 	httprateredis "github.com/go-chi/httprate-redis"
+	"github.com/go-chi/telemetry"
 )
 
 func main() {
 	r := chi.NewRouter()
 	r.Use(middleware.Logger)
 
+	// Expose Prometheus endpoint at /metrics path.
+	r.Use(telemetry.Collector(telemetry.Config{AllowAny: true}))
+
+	rc, _ := httprateredis.NewRedisLimitCounter(&httprateredis.Config{
+		Host: "127.0.0.1", Port: 6379,
+	})
+
 	r.Group(func(r chi.Router) {
+		// Set an extra header demonstrating which backend is currently
+		// in use (redis vs. local in-memory fallback).
+		r.Use(func(next http.Handler) http.Handler {
+			return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				if rc.IsFallbackActivated() {
+					w.Header().Set("X-RateLimit-Backend", "in-memory")
+				} else {
+					w.Header().Set("X-RateLimit-Backend", "redis")
+				}
+				next.ServeHTTP(w, r)
+			})
+		})
+
+		// Rate-limit at 50 req/s per IP address.
 		r.Use(httprate.Limit(
-			5,
-			time.Minute,
+			50, time.Second,
 			httprate.WithKeyByIP(),
 			httprateredis.WithRedisLimitCounter(&httprateredis.Config{
 				Host: "127.0.0.1", Port: 6379,
 			}),
+			httprate.WithLimitCounter(rc),
 		))
 
 		r.Get("/", func(w http.ResponseWriter, r *http.Request) {
-			w.Write([]byte("5 req/min\n"))
+			w.Write([]byte("ok\n"))
 		})
 	})
 
-	log.Printf("Serving at localhost:3333")
+	log.Printf("Serving at http://localhost:3333, rate-limited at 50 req/s per IP address")
 	log.Println()
-	log.Printf("Try running:")
-	log.Printf("curl -v http://localhost:3333")
+	log.Printf("Try making 55 requests:")
+	log.Println(`curl -s -o /dev/null -w "Request #%{xfer_id} => Response HTTP %{http_code} (backend: %header{X-Ratelimit-Backend}, limit: %header{X-Ratelimit-Limit}, remaining: %header{X-Ratelimit-Remaining})\n" "http://localhost:3333?req=[0-54]"`)
 
 	http.ListenAndServe(":3333", r)
 }

config.go

@@ -0,0 +1,36 @@
+package httprateredis
+
+import (
+	"time"
+
+	"github.com/redis/go-redis/v9"
+)
+
+type Config struct {
+	Disabled bool `toml:"disabled"` // default: false
+
+	WindowLength time.Duration `toml:"window_length"` // default: 1m
+	ClientName   string        `toml:"client_name"`   // default: os.Args[0]
+	PrefixKey    string        `toml:"prefix_key"`    // default: "httprate"
+
+	// Disable the use of the local in-memory fallback mechanism. When enabled,
+	// the system will return HTTP 428 for all requests when Redis is down.
+	FallbackDisabled bool `toml:"fallback_disabled"` // default: false
+
+	// Timeout for each Redis command after which we fall back to a local
+	// in-memory counter. If Redis does not respond within this duration,
+	// the system will use the local counter unless it is explicitly disabled.
+	FallbackTimeout time.Duration `toml:"fallback_timeout"` // default: 50ms
+
+	// Client if supplied will be used and the below fields will be ignored.
+	//
+	// NOTE: It's recommended to set short dial/read/write timeouts and disable
+	// retries on the client, so the local in-memory fallback can activate quickly.
+	Client    *redis.Client `toml:"-"`
+	Host      string        `toml:"host"`
+	Port      uint16        `toml:"port"`
+	Password  string        `toml:"password"`   // optional
+	DBIndex   int           `toml:"db_index"`   // default: 0
+	MaxIdle   int           `toml:"max_idle"`   // default: 4
+	MaxActive int           `toml:"max_active"` // default: 8
+}

go.mod

@@ -3,12 +3,12 @@ module github.com/go-chi/httprate-redis
 go 1.19
 
 require (
-	github.com/go-chi/httprate v0.9.0
-	github.com/redis/go-redis/v9 v9.6.0
+	github.com/go-chi/httprate v0.12.0
+	github.com/redis/go-redis/v9 v9.6.1
+	golang.org/x/sync v0.7.0
 )
 
 require (
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f // indirect
-	golang.org/x/sync v0.7.0 // indirect
 )

go.sum

@@ -1,18 +1,14 @@
 github.com/bsm/ginkgo/v2 v2.12.0 h1:Ny8MWAHyOepLGlLKYmXG4IEkioBysk6GpaRTLC8zwWs=
 github.com/bsm/gomega v1.27.10 h1:yeMWxP2pV2fG3FgAODIY8EiRE3dy0aeFYt4l7wh6yKA=
-github.com/cespare/xxhash/v2 v2.2.0 h1:DC2CZ1Ep5Y4k3ZQ899DldepgrayRUGE6BBZ/cd9Cj44=
-github.com/cespare/xxhash/v2 v2.2.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
 github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
 github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f h1:lO4WD4F/rVNCu3HqELle0jiPLLBs70cWOduZpkS1E78=
 github.com/dgryski/go-rendezvous v0.0.0-20200823014737-9f7001d12a5f/go.mod h1:cuUVRXasLTGF7a8hSLbxyZXjz+1KgoB3wDUb6vlszIc=
-github.com/go-chi/httprate v0.8.0 h1:CyKng28yhGnlGXH9EDGC/Qizj29afJQSNW15W/yj34o=
-github.com/go-chi/httprate v0.8.0/go.mod h1:6GOYBSwnpra4CQfAKXu8sQZg+nZ0M1g9QnyFvxrAB8A=
-github.com/go-chi/httprate v0.9.0 h1:21A+4WDMDA5FyWcg7mNrhj63aNT8CGh+Z1alOE/piU8=
-github.com/go-chi/httprate v0.9.0/go.mod h1:6GOYBSwnpra4CQfAKXu8sQZg+nZ0M1g9QnyFvxrAB8A=
-github.com/redis/go-redis/v9 v9.3.0 h1:RiVDjmig62jIWp7Kk4XVLs0hzV6pI3PyTnnL0cnn0u0=
-github.com/redis/go-redis/v9 v9.3.0/go.mod h1:hdY0cQFCN4fnSYT6TkisLufl/4W5UIXyv0b/CLO2V2M=
+github.com/go-chi/httprate v0.12.0 h1:08D/te3pOTJe5+VAZTQrHxwdsH2NyliiUoRD1naKaMg=
+github.com/go-chi/httprate v0.12.0/go.mod h1:TUepLXaz/pCjmCtf/obgOQJ2Sz6rC8fSf5cAt5cnTt0=
 github.com/redis/go-redis/v9 v9.6.0 h1:NLck+Rab3AOTHw21CGRpvQpgTrAU4sgdCswqGtlhGRA=
 github.com/redis/go-redis/v9 v9.6.0/go.mod h1:hdY0cQFCN4fnSYT6TkisLufl/4W5UIXyv0b/CLO2V2M=
+github.com/redis/go-redis/v9 v9.6.1 h1:HHDteefn6ZkTtY5fGUE8tj8uy85AHk6zP7CpzIAM0y4=
+github.com/redis/go-redis/v9 v9.6.1/go.mod h1:0C0c6ycQsdpVNQpxb1njEQIqkx5UcsM8FJCQLgE9+RA=
 golang.org/x/sync v0.7.0 h1:YsImfSBoP9QPYL0xyKJPq0gcaJdG3rInoqxTWbfQu9M=
 golang.org/x/sync v0.7.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=